Aircraft Electronics Cooling Apparatus For An Aircraft Having A Liquid Cooling System

ABSTRACT

The invention relates to an improved aircraft electronics cooling system for an aircraft having a liquid cooling system ( 2 ), the aircraft electronics cooling system providing a thermal coupling between an electronic device ( 40   a,    40   b,    40   c,    40   d,    42, 44 ) to be cooled and the liquid cooling system ( 2 ) of the aircraft. A coolant delivered by the liquid cooling system ( 2 ) may flow through a board of the electronic device ( 40   a,    40   b,    40   c,    40   d ), through a heat sink on which the electronic device ( 42 ) is arranged and/or through a housing in which the electronic device ( 44 ) is arranged. The coolant may be permanently in the liquid state in a cooling circuit. The coolant may vaporise at least partially while cooling the electronic device.

Aircraft manufacturers and operators utilise a continuously increasingnumber of electronic assemblies in aircraft. The electronic assembliesenhance comfort in the cabin on the one hand and aircraft safety on theother. The electronic assemblies generate waste heat and must be cooledin order to function reliably. The air-conditioning apparatus ofconventional aircraft are unable, or only partly able, to meet theseadditional cooling demands.

In conventional aircraft the electronic devices are so designed thateither they must be cooled only by free convection, that is, an air flowis established only through density differences of the air and thuscools the components of the electronic device which are heating up, oradditional fans which generate forced convention are provided.Additional cooling capacity for cooling the electronic devices can bemade available at present only by an air-conditioning system and withthe use of corresponding, weight-increasing conduits.

As previously mentioned, cooling of electronic devices and theircomponents may be effected by means of natural convection. For thispurpose the components are designed correspondingly, or fin-like heatsinks, intended to ensure adequate cooling by means of a correspondinglylarge surface area, are attached thereto. Cooling of the electronicdevices and their components is provided either through the alreadyexisting air-conditioning system, which is used, for example, forcooling the cabin of the aircraft, or an additional air-conditioningsystem is provided.

With the aforementioned methods the electronic devices and theircomponents must be so constructed, as early as the design stage thereof,that they withstand the demanding thermal conditions in an aircraft byheat radiation or natural convection. To increase the heat transfer,fans which draw air from the surroundings may be used. With a high cabintemperature, this cooling is frequently insufficient to transport awaythe heat load generated by the electronic devices. A furtherdisadvantage of these aforementioned methods is that the fan itselfgenerates heat and the mere circulation of the air heats theinstallation space for the electronic devices, too. The aforementionedmethods are unable to cope with larger heat loads of the kind which canbe produced by future electronic devices with increased performance.

Cooling of the electronic devices with the aircraft air-conditioningsystem requires a large amount of space and is insufficiently flexible.The aircraft air-conditioning system has to cool the air provided forcooling the electronic devices. Air supply ducts must be installed inthe aircraft from the aircraft air-conditioning system to the electronicdevices to be cooled, together with air discharge duds from theelectronic devices to be cooled to the aircraft air-conditioning system.Depending on the installation position of the electronics, for example,below the cockpit, if the electronic devices of the aircraft arearranged in that location, the installation of such air supply anddischarge ducts can be complex and costly and, furthermore, can requireinstallation space which consequently is not available for otherfunctions. With such long air supply ducts, high thermal and pneumaticlosses occur which must be compensated by correspondingly higherperformance of the air-conditioning system. This results, inter alia, inthe lack of flexibility of these methods. Furthermore, the spaceconditions prevailing in the aircraft fuselage oppose the use of theaircraft air-conditioning system for cooling the electronic device. Inaddition, the performance of an aircraft air-conditioning system will beunable to meet the future demands for cooling electronic devices.

DE 103 33 353 A1 discloses a system in which a plurality of electronicdevices are cooled with air.

It is an object of the invention to provide an improved cooling of anelectronic device of an aircraft.

This object is achieved by an aircraft electronics cooling apparatus foran aircraft having a liquid cooling system, the aircraft electronicscooling apparatus providing, by means of a coolant circulating in acooling circuit, a thermal coupling between an electronic device to becooled and the liquid cooling system of the aircraft which delivers thecoolant. The coolant delivered by the liquid cooling system may bepermanently in the liquid state in the cooling circuit. However, theaircraft electronics cooling apparatus may also be so configured suchthat the coolant delivered by the liquid cooling system vaporises atleast partially while cooling the electronic device. In the context ofthis description a liquid cooling system is a system which delivers acooled liquid coolant and re-cools a coolant returned from a device tobe cooled, in order to deliver it again as a cooled liquid coolant. Anelectronic device may be a circuit board or a single component, forexample, a power transistor.

Liquid cooling systems with which, for example, food containers can becooled in the galley areas of an aircraft are being increasingly used inaircraft. With such a liquid cooling system, pump devices and coolingdevices are arranged in an underfloor area, for example, in the cargohold, which devices supply heat exchangers installed in the galley areaswith coolant via conduits. These heat exchangers then supply the foodcontainers with cold air and provide corresponding cooling for the food.

It is now proposed according to the invention to use such a liquidcooling system for cooling electronic devices in the aircraft. Thisresults in a smaller mass increase of the aircraft, as compared to aconventional cooling system which supplies cold air to the electronicdevices to be cooled, although the opposite might be expected by aperson skilled in the art. With a liquid-based aircraft electronicscooling apparatus, conduits with a smaller cross-section can be usedbecause far larger quantities of heat can be transported away with aliquid coolant than with a gaseous coolant. The space requirement of theaircraft electronics cooling apparatus is thereby reduced. In addition,the liquid coolant makes possible higher heat transfer coefficients thana gaseous coolant. Because of the smaller cross-section of the coolantconduits, the coolant conduits of a liquid cooling system can beinstalled in the aircraft in a more flexible way, that is, with fewerrestrictions, and sites can be provided with a high cooling capacitywhich could not be provided with such a high cooling capacity by aconventional air-conditioning system.

The aircraft electronics cooling apparatus may include a heat exchangerof a first type through which flow the coolant of a liquid coolingsystem and air which is to be cooled by the coolant, the cooled air thenbeing directed on to the electronic device to be cooled. The heatexchanger is arranged in proximity to the electronic device and the coldair delivered by the heat exchanger can move to the electronic device tobe cooled through natural convection or with the aid of a fan.

The aircraft electronics cooling apparatus may include a heat exchangerof the first type through which flow the coolant of the liquid coolingsystem and air which is to be cooled by the coolant, the air to becooled passing over the electronic device before it enters the heatexchanger of the first type. The air enters the aircraft electronicscooling apparatus, passes the electronic device to be cooled and iscooled in the heat exchanger. In some applications air at the usualcabin air temperature may be sufficient to cool the electronics of anaircraft. Cabin air flows through air inlets to the components, coolingthem convectively, for example. The flow of the air over the electronicdevice may also be supported by a fan and/or forced. The heated air isthen cooled to the cabin air temperature by the heat exchanger of theliquid cooling system and returned to the cabin. This gives rise in theaircraft cabin to a temperature compensation process which does notthermally influence the air-conditioning of the cabin. An advantage ofsuch an aircraft electronics cooling apparatus is that no cold zones,which tend to form condensate, are produced on the electronic device tobe cooled or the component to be cooled. Accumulating condensate couldcause failure of a component of the electronic device or of the wholeelectronic device.

The aircraft electronics cooling apparatus may also cool at least oneelectronic device which is arranged in a housing, the aircraftelectronics cooling apparatus including a heat exchanger of a secondtype arranged in the housing below the at least one electronic device,which heat exchanger of the second type is spaced from the at least oneelectronic device, and at least one opening respectively for inflow oroutflow of air being arranged above the at least one electronic deviceand below the heat exchanger of the second type. Convective coolingthrough free convection thereby takes place. Because of the densitydifferences between cold and warm air, the warm air flows out of the topof the housing. The ambient air flows from below through the housingopenings, via the heat exchanger of the second type connected to theliquid cooling system, to the at least one electronic device to becooled and its components.

A fan operated in such a way that it generates an air flow from the heatexchanger of the second type to the at least one electronic device maybe arranged, for example, between the heat exchanger of the second typeand the at least one electronic device. The cooling capacity of theaircraft cooling system is increased by the air flow generated by thefan.

The electronic device may include a board on which a plurality ofelectronic components are arranged. The aircraft electronics coolingapparatus may be so configured that the coolant of the liquid coolingsystem flows through the board. In this case the board itself forms theheat exchanger. The components may be so constructed that they include aheat exchanger through which the coolant flows. In these configurationsthe heat load can be dissipated directly, that is, without priortransfer of the refrigerating capacity of the liquid cooling system toair.

The electronic device may be arranged in a housing. The aircraftelectronics cooling apparatus may be so configured that the housing isat least partially cooled by the coolant of the liquid cooling system. Acooled environment uncoupled from external conditions is therebycreated.

The electronic device to be cooled may be arranged on a heat sink, forexample by means of its board. The aircraft electronics coolingapparatus may be so configured that the coolant of the liquid coolingsystem flows through the heat sink. In this configuration the electronicdevice can be exchanged without the need to open the heat sink. Aplurality of electronic devices may be arranged on the heat sink, withtheir boards, for example. The boards of the electronic devices may bearranged, for example, on the upper, lower or side faces of the heatsink.

The aircraft electronics cooling apparatus may be so configured that thecoolant of the liquid cooling system flows around the electronic device.For this purpose the electronic devices are arranged in a sealed and/orisolated housing. The housing is connected to the liquid cooling systemvia an inlet opening and an outlet opening and can then be flooded withthe coolant in operation. This presupposes, however, that the coolant isnot affecting the operation of the electronic device or its components.This requirement is met, for example, by a dielectric cooling liquidand/or an electrically non-conductive cooling liquid.

The coolant of the liquid cooling system may flow in a cooling circuitsuccessively and/or in parallel through a plurality of the previouslydescribed configurations of the aircraft electronics cooling apparatus.For example, the coolant of the liquid cooling system may flow in thecooling circuit successively and/or in parallel through at least oneheat exchanger of the first type, through which flow the coolant of theliquid cooling system and air which is cooled by the coolant, the cooledair being directed on to the electronic device to be cooled. The coolantmay additionally flow in the cooling circuit successively and/or inparallel through a heat exchanger of the first type, through which flowthe coolant of the liquid cooling system and air which is cooled by thecoolant, wherein the air to be cooled entering the aircraft electronicscooling apparatus passes the electronic device to be cooled beforeentering the heat exchanger of the first type. The coolant mayadditionally flow in the cooling circuit successively and/or in parallelthrough at least one board of the electronic device. The coolant mayadditionally flow in the cooling circuit successively and/or in parallelthrough at least one heat exchanger of the second type which is arrangedin a housing below an at least one electronic device and spacedtherefrom, at least one respective opening for inflow or outflow of airbeing arranged above the at least one electronic device and below theheat exchanger of the second type. In addition, the coolant may flow inthe cooling circuit successively and/or in parallel on the outer regionof at least one housing in which the electronic device is arranged. Thecoolant may additionally flow in the cooling circuit successively and/orin parallel through at least one heat sink on which the electronicdevice to be cooled is arranged, for example, by means of its board. Thecoolant may also flow in the cooling circuit successively and/or inparallel around at least one electronic device. The coolant cantherefore flow in a cooling circuit through the previously describedconfigurations of an aircraft electronics cooling apparatus successivelyor in parallel in any desired combination.

The invention further provides an aircraft electronics cooling apparatusfor an aircraft having a liquid cooling system, the aircraft electronicscooling apparatus being so configured that the coolant coolssuccessively and/or in parallel through a plurality of electronicdevices and the coolant is permanently in the liquid state. Therefrigerating source of the liquid cooling system may be remote from theelectronic devices. Two liquid cooling systems may be present in theaircraft. One of the liquid cooling systems cools a first number ofelectronic devices. The other liquid cooling system cools a secondnumber of electronic devices. The first number of electronic devices isredundant with respect to the second number of electronic devices. Thisaircraft electronics cooling apparatus may utilise the previouslydescribed heat exchangers or one of the previously described thermalcouplings between the electronic device to be cooled and the coolant.

The invention further relates to a method for cooling an electronicdevice in an aircraft having a liquid cooling system, the methodincluding the step of thermally coupling the liquid cooling systemdelivering a coolant to the electronic device by means of a coolingcircuit. The coolant delivered by the liquid cooling system may bepermanently in the liquid state in the cooling circuit. The coolantdelivered by the liquid cooling system may vaporise at least partiallywhile cooling the electronic device. The method may be furtherconfigured as previously described.

The invention further relates to the use of a liquid cooling system ofan aircraft delivering a coolant for cooling an electronic device in anaircraft by means of a coolant circuit. The coolant delivered by theliquid cooling system may be permanently in the liquid state in thecooling circuit. It is to be understood that the coolant delivered bythe liquid cooling system may vaporise at least partially while coolingthe electronic device. These aspects of the invention may be furtherconfigured as described previously.

The inventive liquid cooling system provides additional cooling capacityfor the electronic devices in an aircraft. Especially when high demandsare placed on the cooling system by the cabin, the liquid cooling systemcan ensure sufficient cooling of the electronic devices. Moreover, theliquid cooling system can cover a relatively wide temperature range andprovide cooling for relatively large thermal loads. Through the use ofthe liquid cooling system for cooling electronic devices, efficientcooling of the electronic devices is ensured in combination with reducedweight. In case a liquid cooling system already exists, practicallyevery region of the aircraft can be reached in a space-saving andflexible way. Because the temperature level of a liquid cooling systemis usually lower than is required for cooling an electronic device, thereturn flow from other heat exchangers, for example, a heat exchanger inthe onboard galley, may also be used for cooling said electronic device.

The invention will now be explained in more detail with reference to theappended schematic Figures, in which:

FIG. 1 shows a first embodiment of the invention, in which air cooled bymeans of a liquid cooling system is directed on to an electronic device;

FIG. 2 shows a second embodiment of the invention, in which air flowsover an electronic device and is then cooled by a liquid cooling system;

FIG. 3 shows a third embodiment of the invention, in which coolant issupplied by a liquid cooling system to a heat exchanger in a housingwith a plurality of electronic devices arranged one above the other;

FIG. 4 shows a fourth embodiment of the invention similar to the thirdembodiment, in which a fan is arranged in the housing above the heatexchanger;

FIG. 5 shows a fifth embodiment of the invention, in which coolant flowsthrough a board of an electronic device;

FIG. 6 shows a sixth embodiment of the invention, in which coolant flowsin the outer region of a housing in which an electronic device isarranged;

FIG. 7 shows a seventh embodiment of the invention, in which theelectronic device is arranged on a heat sink through which coolantflows;

FIG. 8 shows an eighth embodiment of the invention similar to theseventh embodiment, in which a plurality of electronic devices arearranged on the heat sink;

FIG. 9 shows a ninth embodiment of the invention, in which coolant flowsaround an electronic device, and

FIG. 10 shows a tenth embodiment of the invention, in which a pluralityof electronic devices are cooled successively or in parallel in acooling circuit.

FIG. 1 shows a liquid cooling system 2 which supplies coolant to a heatexchanger 8 via a feed line 4, which coolant is returned from the heatexchanger 8 to the liquid cooling system 2 via a return line 6. Theliquid cooling system 2 cools the coolant and delivers it again. In theresulting cooling circuit the coolant is permanently in the liquidstate. It is to be understood that in a different embodiment the coolantmay vaporise at least partially in the heat exchanger 8. The heatexchanger 8 draws in warm air via an intake conduit 12, which warm airis cooled as it passes through the heat exchanger 8, and is directed bya discharge conduit 10 on to an electronic device 14 with a plurality ofcomponents. In this embodiment the electronic device 14 and itscomponents 16 are cooled convectively. The heat exchanger 8 is locatedin proximity to the electronic device 14, so that only a short intakeconduit 12 and discharge conduit 10 are required. The air exiting theheat exchanger 8 may cool a plurality of electronic devices 14.

FIG. 2 shows a further embodiment of the aircraft electronics coolingapparatus. A liquid cooling system 2 supplies coolant to a heatexchanger 8 via a feed line 4, which coolant is returned to the liquidcooling system 2 via a return line 6. Air from the cabin at cabin airtemperature enters a housing 18 via at least one opening 20 in thehousing 18, in which an electronic device 14 with a plurality ofelectronic components 16 is arranged. The air flows past the components16 of the electronic device 14, cooling the components 16 and the wholeelectronic device 14. The air flowing past the electronic device 14enters the heat exchanger via an intake conduit 12, is cooled in theheat exchanger to the cabin air temperature and re-enters the cabin viaa discharge conduit 10. In some applications the usual cabin airtemperature in an aircraft is sufficient to cool an electronic device.In this embodiment a neutral temperature compensation process which doesnot thermally influence the cabin air-conditioning system is producedfor the aircraft cabin. An advantage of this embodiment is that no coldzones, on which condensate can collect, are produced on the electronicdevice 14 and/or on its components 16. Condensate can cause failure of acomponent 16 or of the electronic device 14. The air entering the heatexchanger 8 may cool a plurality of electronic devices 14.

FIG. 3 shows a third embodiment of the inventive aircraft electronicscooling apparatus. A plurality of electronic devices 14 with a pluralityof electronic components 16 are arranged in a housing 22. At least onelower opening 26 is located in the lower region of the housing 22 and atleast one upper opening 28 is located in the upper region of the housing22. A heat exchanger 24 is arranged between the at least one loweropening 26 and the plurality of electronic devices 14. A liquid coolingsystem 2 supplies coolant to the heat exchanger 24 via a feed line 4,which coolant is returned to the liquid cooling system 2 via a returnline 6. In this embodiment cooling takes place by free convection. Thewarm air with low density exits the housing 22 through the plurality ofupper openings 28. At the same time air enters through the plurality oflower openings 26 of the housing 22, is cooled by the heat exchanger 24and flows to the electronic devices 14 and their components 16 to becooled.

FIG. 4 shows a fourth embodiment of the inventive aircraftair-conditioning system which is similar to the embodiment of FIG. 3 andadditionally includes a fan 30 which is arranged in the housing 22between the heat exchanger 24 and the plurality of electronic devices 14with a plurality of components 14. The fan 30 generates an air flowwhich is directed towards the electronic devices 14 to be cooled. Airenters the housing via the plurality of lower openings 26, passesthrough the heat exchanger 24 and flows around the electronic devices 14and their components 16 in order to cool same, and exits the housing 22through the upper openings 28.

FIG. 5 shows a fifth embodiment of the inventive aircraft electronicscooling apparatus. An electronic device 14 comprises a plurality ofcomponents 16 which are arranged on a board 32. The board 32 is in theform of a heat exchanger and coolant flows at least partially throughsaid heat exchanger. A liquid cooling system 2 supplies coolant to theboard 32 via a feed line 4, which coolant cools the components 16arranged on the board 32. The coolant may also flow through at least onecomponent 16 which is arranged on the board 32. The coolant exits theboard into a return line 6 and is returned to the liquid cooling system2.

FIG. 6 shows a sixth embodiment of the inventive aircraft electronicscooling assembly, in which an electronic device with a plurality ofcomponents 16 is arranged in a housing 34. Coolant flows at leastpartially through the outer region of the housing 34, or at least ahousing wall. A liquid cooling system 2 supplies coolant via a feed line4 to the housing 34. The housing and also the electronic device 14 inthe housing are thereby cooled. The coolant exits the housing 34 into areturn line 6 and is returned to the liquid cooling system. In thisembodiment the electronic device 14 is completely uncoupled from theenvironment. This embodiment may be used with electronic devices whichmust ensure especially high security against failure and/or whichcontrol or monitor safety-relevant functions.

FIG. 7 shows a seventh embodiment of the invention, in which anelectronic device 14 is arranged on a heat sink 36, e.g. a cooling body.FIG. 8 shows an eighth embodiment of the invention, in which a pluralityof electronic devices 14, 14 a, 14 b are arranged on a heat sink 36 a. Aliquid cooling system 2 supplies coolant via a feed line 4 to the heatsink 36, 36 a, on which at least one electronic device 14, 14 a, 14 b isarranged. The heat sink extracts heat from the at least one electronicdevice 14, 14 a, 14 b and dissipates it to the coolant. The coolantflows back to the liquid cooling system 2 via a return line 6. Theseembodiments have the advantage that it is not necessary to open thecooling circuit in order to exchange the electronic device 14, 14 a, 14b. This gives rise to an aircraft electronics cooling apparatus which isespecially maintenance-friendly. However, it is not ruled out in theseembodiments that individual components 16 are supplied with coolantseparately.

FIG. 9 shows a ninth embodiment of the inventive aircraft electronicscooling apparatus, in which an electronic device is arranged in ahousing 38, the coolant flowing through the interior of the housing 38.A liquid cooling system 2 supplies coolant to the housing 38 via a feedline 4. In the interior of the housing 38 the coolant flows around theelectronic device and its components 16. However, the electronic device14 may also be sealed, so that the components 16 do not come intocontact with the coolant. The coolant extracts heat from the electronicdevice 14 and its components 16, respectively, and flows back to theliquid cooling system 2 via a return line 6. In this embodiment anespecially large amount of heat is extracted from the electronic device14 and its components 16, so that this embodiment is especially suitablefor electronic devices which must provide high electronic performance orhave high power dissipation. In this embodiment the electronic devicemust be so constructed that the coolant has no influence on theoperability of the electronic device. This requirement is met, forexample, by a dielectric cooling liquid and/or an electricallynon-conductive cooling liquid.

FIG. 10 shows an inventive aircraft electronics cooling apparatus inwhich the coolant provides cooling in series and in parallel to aplurality of electronic devices in a cooling circuit. Via a feed line 4a liquid cooling system 2 supplies coolant in parallel to a plurality ofelectronic devices 40 a, 40 b, 40 c, through the boards of which coolantflows, as explained previously with reference to the fifth embodiment.The coolant flows through the plurality of electronic devices 40 a, 40b, 40 c in parallel, ensuring higher redundancy and security againstfailure The coolant also flows to an electronic device 42 which isarranged on a heat sink through which coolant flows, as explainedpreviously with reference to the seventh embodiment. The coolant thenflows into the outer region of a housing in which an electronic device44 is located, as explained previously with reference to the sixthembodiment. The coolant then flows to a further electronic device 40 dwhich is so configured that the coolant can flow through the boardthereof in order to cool the electronic device 40 d, as explainedpreviously with reference to the fifth embodiment. The coolant thenflows back to the liquid cooling system 2 via a return line 6. Theelectronic devices 42, 44, 40 d connected in series to one another maybe located at different sites in the aircraft. Because of the highflexibility of the inventive aircraft electronics cooling apparatus,electronic devices which are located at practically any desired site inthe aircraft can be cooled. It is to be understood that, in order toincrease the safety and redundancy of the inventive aircraft electronicscooling apparatus, all the electronic devices may also be supplied withcoolant in parallel.

The coolant utilised in the aircraft electronics cooling apparatus ispreferably a dielectric liquid. The dielectric liquid does not affectthe operation of the electronic devices and their components. Thecoolant preferably has a temperature from approximately +10° C. toapproximately +20° C. An example of a dielectric liquid is Galden® HT135 or ZT 130 of Solvay Solexis.

In an embodiment the coolant delivered by the liquid cooling system maybe permanently in the liquid state. In this embodiment thermodynamicparameters such as boiling temperature and the like do not need to beconsidered. Moreover, in this embodiment, as explained previously, aplurality of electronic devices to be cooled may be located serially ina cooling circuit.

In another embodiment, however, the aircraft electronics coolingapparatus may be so configured that the coolant delivered by the liquidcooling system vaporises at least partially while cooling the electronicdevice. With this embodiment higher cooling capacities can be achievedand larger quantities of heat transported away.

1. Aircraft electronics cooling apparatus for an aircraft having a liquid cooling system, characterised in that the aircraft electronics cooling apparatus provides, by means of a coolant circulating in a cooling circuit, a thermal coupling between an electronic device to be cooled and the liquid cooling system which delivers the coolant.
 2. Aircraft electronics cooling apparatus according to claim 1, characterised in that the coolant delivered by the liquid cooling system is permanently in the liquid state in the cooling circuit.
 3. Aircraft electronics cooling apparatus according to claim 1, characterised in that the aircraft electronics cooling apparatus is configured such that the coolant delivered by the liquid cooling system vaporises at least partially while cooling the electronic device.
 4. Aircraft electronics cooling apparatus according to claim 1, characterised in that the aircraft electronics cooling apparatus includes a heat exchanger of a first type through which flow the coolant of the liquid cooling system and air which is cooled by the coolant, the cooled air being directed to the electronic device to be cooled.
 5. Aircraft electronics cooling apparatus according to claim 1, characterised in that the aircraft electronics cooling apparatus includes a heat exchanger of a first type through which flow the coolant of the liquid cooling system and air which is cooled by the coolant, wherein the air entering the aircraft electronics cooling apparatus passes the electronic device to be cooled before entering the heat exchanger of the first type.
 6. Aircraft electronics cooling apparatus according to claim 1, characterised in that at least one electronic device to be cooled is arranged in a housing, the aircraft electronics cooling apparatus includes a heat exchanger of a second type arranged in the housing below the at least one electronic device to be cooled, which heat exchanger of the second type is spaced from the at least one electronic device, and at least one respective opening for outflow of air is arranged above the at least one electronic device to be cooled and at least one respective opening for inflow is arranged below the heat exchanger of the second type.
 7. Aircraft electronics cooling apparatus according to claim 6, characterised in that the aircraft electronics cooling apparatus includes a fan which is operated such that it generates an air flow from the heat exchanger of the second type to the at least one electronic device to be cooled.
 8. Aircraft electronics cooling apparatus according to claim 1, characterised in that the electronic device to be cooled includes a board, the aircraft electronics cooling apparatus being configured such that the coolant of the liquid cooling system flows through the board.
 9. Aircraft electronics cooling apparatus according to claim 1, characterised in that the electronic device to be cooled is arranged in a housing, the aircraft electronics cooling apparatus being configured such that the housing is cooled at least partially by the coolant of the liquid cooling system.
 10. Aircraft electronics cooling apparatus according to claim 1, characterised in that the electronic device to be cooled is arranged with the board thereof on a heat sink, the aircraft electronics cooling apparatus being configured such that the coolant of the liquid cooling system flows through the heat sink.
 11. Aircraft electronics cooling apparatus according to claim 1, characterised in that the aircraft electronics cooling apparatus is configured such that the coolant of the liquid cooling system flows around the electronic device to be cooled.
 12. Aircraft electronics cooling apparatus according to claim 1, characterised in that the aircraft electronics cooling apparatus is configured such that the coolant in the cooling circuit flows serially and/or in parallel at least: through a heat exchanger of the first type through which flow the coolant of the liquid cooling system and air which is cooled by the coolant, the cooled air being directed on to the electronic device to be cooled, through a heat exchanger of the first type through which flow the coolant of the liquid cooling system and air which is cooled by the coolant, wherein the air entering the aircraft electronics cooling apparatus passes the electronic device to be cooled before entering the heat exchanger of the first type, through a board of the electronic device to be cooled, through a heat exchanger of the second type which is arranged in a housing below at least one electronic device to be cooled and is spaced therefrom, wherein at least one respective opening for outflow of air is arranged above the electronic devices to be cooled and below the heat exchanger of the second type is arranged at least one respective opening for inflow, through the outer region of a housing in which the electronic device to be cooled is arranged, through a heat sink on which the electronic device to be cooled is arranged, and/or around the electronic device to be cooled.
 13. Aircraft electronics cooling apparatus according to claim 1, characterised in that the coolant delivered by the liquid cooling system is a dielectric liquid and/or an electrically non-conductive liquid.
 14. Aircraft electronics cooling apparatus for an aircraft having a liquid cooling system, wherein the aircraft electronics cooling apparatus is configured such that the coolant cools a plurality of electronic devices serially and/or in parallel and the coolant is permanently in the liquid state.
 15. Aircraft electronics cooling apparatus, wherein the aircraft electronics cooling apparatus is configured such that the coolant in the cooling circuit flows serially and/or in parallel at least: through a heat exchanger of the first type through which flow the coolant of the liquid cooling system and air which is cooled by the coolant, the cooled air being directed to the electronic device to be cooled, through a heat exchanger of the first type through which flow the coolant of the liquid cooling system and which is cooled by the coolant, wherein the air entering the aircraft electronics cooling apparatus passes the electronic device to be cooled before entering the heat exchanger of the first type, through a board of the electronic device to be cooled, through a heat exchanger of the second type which is arranged in a housing below at least one electronic device to be cooled and is spaced therefrom, wherein at least one respective opening for outflow of air is arranged above the electronic devices to be cooled and below the heat exchanger of the second type is arranged at least one respective opening for inflow, through the outer region of a housing in which the electronic device to be cooled is arranged, through a heat sink on which the electronic device to be cooled is arranged, and/or around the electronic device to be cooled.
 16. Aircraft electronics cooling apparatus for an aircraft having a liquid cooling system, wherein the aircraft electronics cooling apparatus provides, by means of a coolant circulating in a cooling circuit, a thermal coupling between an electronic device to be cooled and the liquid cooling system which delivers the coolant, wherein the aircraft electronics cooling apparatus comprises a heat exchanger of a first type through which flow the coolant of the liquid cooling system and air which is cooled by the coolant, wherein the air entering the aircraft electronics cooling apparatus passes the electronic device to be cooled before entering the heat exchanger of the first type.
 17. Aircraft electronics cooling apparatus for an aircraft having a liquid cooling system, wherein the aircraft electronics cooling apparatus provides, by means of a coolant circulating in a cooling circuit, a thermal coupling between an electronic device to be cooled and the liquid cooling system which delivers the coolant, wherein the at least one electronic device to be cooled is arranged in a housing, the aircraft electronic cooling apparatus includes a heat exchanger of a second type arranged in the housing below the at least one electronic device to be cooled, which heat exchanger of the second type is spaced from the at least one electronic device, and at least one respective opening for outflow of air is arranged above the at least one electronic device to be cooled and at least one respective opening for inflow is arranged below the heat exchanger of the second type, wherein the air flows through the aircraft electronics cooling apparatus by free convection.
 18. Aircraft electronics cooling apparatus for an aircraft having a liquid cooling system, wherein the aircraft electronics cooling apparatus provides, by means of a coolant circulating in a cooling circuit, a thermal coupling between an electronic device to be cooled and the liquid cooling system which delivers the coolant, wherein the aircraft electronics cooling apparatus is configured such that the coolant of the liquid cooling system flows around the electronic device to be cooled.
 19. Method for cooling an electronic device in an aircraft having a liquid cooling system, characterised by the step of thermally coupling, by means of a cooling circuit, the liquid cooling system, which delivers a coolant, to the electronic device to be cooled.
 20. Method according to claim 19, characterised in that the coolant delivered by the liquid cooling system is permanently in the liquid state in the cooling circuit.
 21. Method according to claim 19, characterised in that the coolant delivered by the liquid cooling system vaporises at least partially while cooling the electronic device.
 22. Use of a liquid cooling system of an aircraft which delivers a coolant for cooling an electronic device in an aircraft by means of a cooling circuit.
 23. Use according to claim 22, characterised in that the coolant delivered by the liquid cooling system is permanently in the liquid state in the cooling circuit.
 24. Use according to claim 22, characterised in that the coolant delivered by the liquid cooling system vaporises at least partially while cooling the electronic device. 